#include <stdio.h>
#include <stdlib.h>

struct time_struct
{
    unsigned char hour;
    unsigned char minute;
    unsigned char second;
};

void show_time(struct time_struct * ptime)
{
    if(ptime->hour < 10)putchar('0');
    printf("%d:",ptime->hour);
    if(ptime->minute < 10)putchar('0');
    printf("%d:",ptime->minute);
    if(ptime->second < 10)putchar('0');
    printf("%d\n",ptime->second);
}

int main()
{
    struct time_struct time = {.hour = 16, .minute = 40, .second = 51};
    show_time(&time);
    return 0;
}